1. Field of the Invention
The present invention relates to an image transmission device and method, a transmitting device and method, a receiving device and method, and robot apparatus, and is suitably applicable to, for example, an entertainment robot.
2. Description of the Related Art
There has been widely used various transmission systems such as International Telecommunication Union (ITU)-R REC656 as a transmission system of an image in image transmission systems such as a Television broadcasting system, a satellite broadcasting system, a Television-phone system, and a surveillance camera system.
In this case, these transmission systems, when image data of multiple channels are transmitted, requires to have multiple transmission lines or have some way for multiplexing each image data of the channels, since these transmission systems are formed on the premise that one image is transmitted via one transmission line.
Here, the first method to have multiple transmission lines as above is to assign separated transmission lines to each channel, and for example, this method is adopted in a surveillance system where multiple surveillance cameras and centers are wired and connected one-on-one. Furthermore, in this first method, format modification of the image data flowing through each of the transmission lines is not required, and therefore this first method has a benefit that existing systems can be used without system modification.
However, by this first method, it is necessary to wire and connect a transmitting side and the corresponding receiving side for each of the channels, and to prepare a new line for a new channel so as to increase the number of the channels, which makes the system construction and modification difficult.
On the other hand, the second method to transmit multiplexed image data of each channel through a single transmission line is widely used in dedicated purpose systems such as the Television broadcasting system, the satellite broadcasting system, and the Television-phone system. There have been known two multiplexing systems, a frequency division multiplexing system and a time division multiplexing system.
In the frequency division multiplexing system of those two systems, frequency bands used for transmission are setup for each channel respectively, and the signal of multiple channels having those different frequency bands are superposed and transmitted, where the receiving side can receive any channel by selecting the frequency band. This system is adopted in the Television broadcasting system and so forth.
In the time division multiplexing system, the image data of multiple channels are quantized at a data level within a frame, are divided, and are delivered, where at the receiving side, the image data of each channel are restored by way of reallocating the image data for each channel in order of arrival. This time division multiplexing system is adopted in the satellite broadcasting system and so forth.
However, since these multiplexing systems require the format modification of the image data on the transmission line, the existing system, which is formed on the premise of transmitting and receiving the image data through a single transmission line, cannot even restore the image with these multiplexing systems. Therefore, when a user of such existing systems newly adopts the above mentioned multiplexing systems, it is required to modify the whole system including receiving devices, cables, and so on.
Specifically in the time division multiplexing system, it is necessary to have the transfer speed of the image data on the transmission line high according to the number of the channels to be multiplexed. The reason is that since, in the image data transmission, the reception of the last image data within one image at the receiving side means the completion of the transmission of one frame of the image, slow transfer speed of the transmission line for the number of the channels to be multiplexed causes a large time-lag until the reception of the image data, which causes a serious problem.
As described above, the proposed multiplexing systems cannot be realized by using the existing image transmission systems which is formed on the premise of transmitting and receiving of the image data through single transmission line, and have the difficulty to be realized by the modification of the existing image transmission systems.